1. Field of the Invention
The invention relates to a fuel cell system used in a fuel cell vehicle, the fuel cell vehicle, and a method of controlling the fuel cell system.
2. Description of Related Art
When a fuel cell is stopped, hydrogen in an anode moves through an electrolyte membrane into a cathode and is retained in the cathode. Japanese Patent Application Publication No. 2008-021485 (JP 2008-021485 A) describes supplying the cathode with an oxidant gas in order to dilute and discharge the hydrogen retained in the cathode. The oxidant gas is supplied by a pump (an air compressor).
However, a fuel cell vehicle does not typically start to run as soon as a starter switch is switched on, and therefore no load demand is issued to the fuel cell. In a condition where no load demand is issued to the fuel cell, it is not preferable, in consideration of fuel efficiency and noise vibration (noise and vibration), to supply the oxidant gas by driving the air compressor merely in order to dilute and discharge the hydrogen retained in the cathode. Moreover, when the oxidant gas is supplied, the fuel cell enters a power generation condition, leading to excessive hydrogen consumption and a corresponding reduction in fuel efficiency.